Geobacters Cleanup Groundwater Contaminated with Uranium

Katie Huston for TEI

Twenty-one years ago, Derek Lovley discovered Geobacters, novel anaerobic organisms that gain energy from iron oxides. Today, he’s as excited about working with them as ever. “[Geobacter] is just so darn interesting,” he says. “It does so many interesting things.”

Lovley, a Distinguished University Professor of Microbiology, first isolated Geobacters in the Potomac River downstream from Washington, D.C., in 1987 while working at a federal government lab. Since then, he’s discovered numerous applications, including bioremediation of polluted groundwater and harvesting electricity from organic waste. Today, among other projects, he’s shifted his focus to treating groundwater that’s been contaminated with uranium. “A lot of groundwater’s contaminated in this country,” he says. “Everybody thinks water’s going to be the next big resource problem.”

Geobacters were the first organisms found to gain energy from iron oxides, rust-like material, in the same way as humans use oxygen. “[It’s] good because in the ground, especially when it’s polluted, there’s no oxygen, but there’s lots of iron,” Lovley says.
Geobacters can also use a number of contaminant organics as food, such as landfill leachate and petroleum-derived aromatic hydrocarbons like benzene or toluene, which gives them a wide range of potential applications.

Lovley and a team of researchers, made up of primarily postdoctoral researchers and graduate students, is currently focusing on Geobacters’ ability to immobilize uranium in groundwater. Uranium contamination is primarily found on federal properties, in places where uranium was mined and processed for nuclear weapons. In addition to being radioactive, uranium is highly toxic and can cause kidney problems. When Geobacters grow on uranium, they can’t take away the radioactivity, Lovley says. However, they can transform uranium from a form that’s soluble in water (which means it can flow through groundwater) into a mineral that falls out of the water and cannot move any further.

Because they are naturally occurring, Geobacters offer a lot of promise for bioremediation. “They’re found everywhere. They’re in most aquatic sediments and submerged soils,” Lovley says. “It’s definitely the best-case scenario. If you had to add the microorganisms, the chance of being able to keep them viable and active would be much less than using naturally-occurring organisms.”

In order to carry out the process effectively, members of the Geobacter Project need to determine precisely how Geobacters work. “A lot of our research is to understand how Geobacter activity could best be stimulated in the ground,” Lovley says. “The idea is if you learn enough about it, we’ll have models to predict before we go to a contaminated site, like what we should add to groundwater to best promote its activity, how fast it will degrade contaminants.”

To understand the organism, Lovley and his team are working on a complete model of the Geobacter genome sequence, which is newly possible through advances in technology. “It tells us the full potential of what Geobacters can do, if we see a gene for a specific activity,” he says. “We also see a lot of genes we don’t know what they do, so we study those. We’re basically trying to decode how it works, and that’s a good place to start, understanding what genes it has.”

Lovley also looks for factors that restrict Geobacters’ growth, which can translate into a lack of vital nutrients, such as nitrogen, phosophorus, iron and sulfur, or an over concentration of salt, acid or toxic metals. “We’re doing a lot of work at a mining site right now. Salt concentration is sometimes too high, or too acid, things like that,” he says. “We try to get an overall scope of that – how it will grow under those conditions, and how we might alleviate it by adding something.”

Lovley doesn’t spend much time in the field anymore, he says. “I specifically went into this field so I could get a job working outside and I barely get to go outside now,” he laughs. But others do. Lovley supervises work that takes place on many levels, bolstered by his team of researchers, which numbers approximately 60. Various members of the Geobacter Project are placed in the field at contaminated sites; work in the lab; study the organism’s function as a whole unit; focus on specific genes; and conduct computer analysis of the genes and their interactions.

Studying bioremediation is a difficult task, Lovley says. “It’s difficult to study the process because you don’t have ready access to the subsurface,” he says. “Everything’s taking place below ground, and you have to query the subsurface by drilling the well in there. You can only drill so many wells, and as soon as you pull some water out you basically disturb the environment, so it’s not exactly the way it is in an undisturbed state.”

Replicating conditions in a lab is also difficult, and natural replication times for Geobacters are slow. “When they’re naturally growing in the environment they might divide once a week or something like that – it’s really slow in the subsurface. In the laboratory we want things to happen quickly so we can get results,” he says. “Can you really extrapolate from what you grow rapidly in the lab? Does that really translate to subsurface conditions?”

Still, Lovley has made great strides in his research since coming to UMass Amherst in 1995. The Geobacter Project has received a steady high level of funding for the past 10 years, and was featured in a recent television ad with Massachusetts Governor Deval Patrick. It all comes down to understanding the microorganisms, Lovley says. “After I graduated from undergrad [at the University of Connecticut], I started to realize that microorganisms were the key drivers in almost all aquatic systems, and that they weren’t well understood at all,” he says. “It’s now understood that [microorganisms] are really important, and there’s a lot better tools for studying them now.”